fixed a bug with prefix; changed approach to alias detection
fixed a bug with prefix; changed approach to alias detection

I didn't realize that prefix could've been a list, which completely breaks the previous code.
Also I changed my approach of detecting aliases so that messages with lots of words doesn't stop so much
Plus, since I'm not monkey patching commands.Command for all recursive names,
I used an alternate way (might be slower to do always tripping the exception) to check if it's an already existing command

Ikusaba-san/Chiaki-Nanami